The dairy, food and pharmaceutical industries use tanks for processing and for storing highly sensitive products. Common preparation processes may include blending, homogenizing, chilling, heating and pasteurizing. Food, cosmetic and pharmacologic ingredients are particularly susceptible to microbial contamination. In addition, process control requires avoiding of any unintended cross-contamination of components from one product type to another. Therefore, thoroughly cleaning of processing tanks between production batches and when changing product type is essential.
An industry standard for apparatus acceptable for use in cleaning process and storage tanks has been developed and is widely used. The standard is titled 3-A® Sanitary Standards for Spray Cleaning Devices Intended to Remain in Place, Number 78-01, as updated periodically (hereafter the 3-A Standard). The accepted 3-A Standard defines design parameters for cleaning apparatus to minimize the chance of the cleaning liquid being retained in the cleaning device, potentially encouraging bacterial growth. Exemplary design parameters include, inter alia, that all surfaces must be self draining and self flushing, all internal corners must be formed with a radius, interior surfaces must be polished, and no machine threads are permitted on any product or solution contacting surface. Acceptable apparatus must be easily disassembled for cleaning and inspection.
Current industry practice for conforming to the 3-A Standard has been to use a “spray ball” apparatus for cleaning tank interiors. A spray ball is essentially a hollow sphere having a pattern of small holes through the surface to function as nozzles and spray a liquid at the interior surface of the tank. The spray ball may be rotated or stationary. Spray balls have the advantage of not having internal moving parts, i.e. requiring little maintenance effort, but having the disadvantage of not being very effective for cleaning the interior walls of a tank.
A more effective cleaning device is the rotary impingement cleaning apparatus that has been used for cleaning industrial storage and process tanks. Examples of known rotary impingement cleaning apparatus are disclosed in U.S. Pat. Nos. 5,169,069 and 6,561,199. However, conventional rotary impingement cleaning apparatus do not conform to the 3-A Standard. A conventional rotary impingement cleaning apparatus typically has a complex internal mechanism, including either a worm gear transmission or a multiple stage planetary gear train, making self draining or self flushing of liquid and other 3-A Standard requirements unattainable.
Therefore, a need exists for an effective cleaning apparatus that conforms to the 3-A Standard for spray cleaning devices. Major considerations in conformity to the 3-A Standard are optimum drainage and flushing of cleaning liquids, and ease of inspection and servicing. The invention disclosed herein provides a cleaning apparatus conforming to the 3-A Standard.